An aircraft is propelled by one or several propulsion assemblies comprising a turbojet engine housed in a tubular nacelle. Each propulsion assembly is attached to the aircraft by an attachment pylon generally situated under a wing or at the fuselage.
A nacelle generally has a structure comprising an air intake upstream of the engine, a central section intended to surround a fan of the turbojet engine, a downstream section housing thrust reverser means and intended to surround the combustion chamber of the turbojet engine.
“Downstream” here refers to the direction corresponding to the direction of the air flow, in particularly of cold air, penetrating the turbojet engine. “Upstream” designates the opposite direction.
The air intake comprises, on one hand, an air intake lip adapted to allow optimal collection towards the turbojet engine of the air necessary to supply the fan and the internal compressors of the turbojet engine, and on the other hand, a downstream structure on which the lip is attached and intended to channel the air suitably towards the vanes of the fan. The assembly is attached upstream of a fan case surrounding the fan belonging to the turbojet engine.
The nacelle houses internal equipment necessary for the operation of the turbojet engine. This internal equipment is housed on a large portion of the length of the nacelle. Thus, upstream of the nacelle, there are deicing systems to prevent frost or ice from forming on the air intake lip and thereby greatly decreasing the performance of the engine. Further downstream, some internal equipment allows the supply and proper operation of the engine.
Currently, maintenance operations on this internal equipment require the builders to provide access hatches. Despite the efforts made to optimize the positioning of the hatches and allow the easiest possible access, it is sometimes necessary to reach said equipment using specific tools, such as an endoscope, which is not fully satisfactory in terms of monitoring this equipment.
Moreover, in the event it is necessary to replace part of the internal equipment, it is generally necessary to take out the entire air intake structure, which requires significant tools and causes immobilization of the propulsion assembly and therefore of the aircraft in general.
It will also be noted that the conditions for exploitation and maintenance of an air intake require distinct components, such as a sectorized modular lip as well as an easily removable outer panel due to their high replacement rate as a result of their direct exposure to the outside environment and any projectiles. These constraints significantly reduce the integrity of the general aerodynamic line of the air intake structure, which the presence of access hatches further aggravates.
Solutions have been presented in document U.S. Pat. No. 5,609,313 and application FR 06/08599. In order to offset the mentioned drawbacks, these documents provide a turbojet engine nacelle comprising an air intake structure that can be translated forward and thereby at least partially exposes the area situated inside the nacelle.
In this way, by incorporating the air intake lip into the outer panel so as to form a single disassemblable piece, disassembly and at least partial replacement of the air intake structure are made easier. As a result, it is possible to access internal equipment without demanding substantial and complicated maneuvers or requiring a long immobilization time.
These mobile cowls are generally mounted on a rail/slide system made up of rails and slides arranged around the nacelle. The rails make it possible to release the assembly formed by the outer panel and the air intake lip to free the zone situated inside the air intake structure. Nevertheless, the internal equipment housed downstream of the air intake structure remains difficult to access.
Application GB 2 274 490 proposes a nacelle in which the outer panel and the air intake lip form a movable structure sliding in the upstream direction of the nacelle via a system of rails. Furthermore, the outer panel covers the inner panel and the fan casing to which the inner panel is attached.
Nevertheless, this type of nacelle can be difficult to manipulate. There is a significant risk of jamming, in particular between the attachment pylon and the outer panel. Furthermore, this type of nacelle is not suitable for nacelles arranged at the fuselage of an aircraft and for which the attachment pylon is substantially horizontal relative to the body of the aircraft. In that case, the thickness of the nacelle is thin with the result that the outer panel can abut against internal equipment present inside the nacelle.